The present invention relates to a drinking water feeding apparatus having a sterilizing function in an automatic vendor, a beverage dispenser, a water cooler, an ice maker or a home water purifier. The invention also relates to a chlorine generator to be used in the drinking water feeding apparatus.
Service water fed to a drinking water feeding apparatus typically may have a chlorine smell or a muddiness and a rust from the piping. If a beverage (e.g. soft drink or coffee) is dispensed using service water as provided, its intrinsic taste or flavor may be unacceptable. In order to satisfy the water quality standards based on the service water regulations, a filter is frequently used. Such filters must have a filtering function, a dechlorinating function and the ability to remove perceived muddiness. Most filters are troubled by bacterial contamination. Carbon type filters are frequently used for drinking water. They have excellent filtering, dechlorinating and muddiness-removing abilities, but the filtering material (carbon) deactivates the active chlorine contained in the service water, so that the filter loses its sterilizing and fungistatic abilities against the bacteria or the like which migrate into the service water.
Under circumstances in which no service water facilities are available, the service water is stored in a tank (cassette tank). In this system, however, it is difficult to keep either the cassette tank itself or the reserved water of the cassette tank which is in contact with the atmosphere in a sanitary state. Furthermore, the filtering material typically has to be replaced when the quantity of the water which has been filtered exceeds a predetermined maximum value. During filter replacement, aerobacteria can migrate into the filter.
Thus, there arises a problem that the inside and the downstream of the filter become hotbeds for the growth of various bacteria. When bacteria are present in concentrations of 15 MPN/100 ml in the service water, for example, they can propagate to concentrations of up to 3.9xc3x97103 cfu/ml after being left for one day at the ambient temperature of 30xc2x0 C., in a filter container of 1 L containing 390 ml activated charcoal, with an 80 ml collecting pipe and 340 ml water in a filter cartridge.
For this reason, methods have been devised to attempt to control the number of bacteria in the filter, in which carbon and a fibrous filter are combined to retain active chlorine. Thus, an effective quantity of active chlorine is fed to the downstream of the filter, providing a sterilizing effect. About one third of the total chlorine ion concentration present in typical feed water would be effective for removing bacteria, but the method is not expected to be sufficiently effective for locations where the chlorine concentration contained in the service water is low or for the service water in which most of the active chlorine is effectively deactivated.
In order to avoid drinking water contamination by the bacteria, a drinking water feeding apparatus is disclosed in Unexamined Published Japanese Patent Application No. 9-1149. This reference discloses a closed-type drinking water feeding apparatus which is constructed to isolate the drinking water pipelines from the atmosphere, thereby preventing possible contamination by aerobacteria. Also inherent in Unexamined Published Japanese Published Japanese Patent Application No. 9-1149, is the difficulty that while air can be removed upstream of the chlorine generator, it cannot be removed from the passage downstream of the chlorine generator. Moreover, as drinking water is electrolyzed in the chlorine generator, oxygen or other gases are generated at the positive electrode, and hydrogen gas is generated at the negative electrode. The generation of these gases leads to a reduction in the electrolysis efficiency of the chlorine generator, such that a desired chlorine concentration necessary for sterilization cannot be achieved. This apparatus generates active chlorine by causing electrodes to contact drinking water as it is fed through a filter and by electrolyzing the drinking water so that the drinking water is sterilized by active chlorine. In order to maintain levels of active chlorine sufficient for sterilization purposes, it was found necessary to elongate the electrode surfaces in the flow stream or, alternatively, to reduce the flow speed of the drinking water through the apparatus. There are several drawbacks to this approach however. An elongation of the electrodes inevitably enlarges the apparatus because the elongated electrodes cannot be accommodated in the limited space of a standard beverage dispenser. Furthermore, reducing the feed rate of the service water unduly limits the dispensing rate of the drinking water.
Another way to generate active chlorine in effective sterilizing concentrations without changing the size of the electrodes or reducing the water flow speed, is to increase the electric current to be applied. In this case, however, as the current density rises, electrode consumption accelerates. In an attempt to minimize consumption of electrodes, therefore, the current value has to be suppressed and the problem arises that a predetermined uniform chlorine concentration value (e. g., 0.2 ppm) cannot be achieved for the drinking water for all the geographic areas having different water qualities. Specifically, the desired chlorine concentration depends mainly on the two parameters: the quality (especially, conductivity and chlorine ion concentration) of water to be electrolyzed; and an xe2x80x9cONxe2x80x9d time period. If the electrodes cannot be enlarged and if the xe2x80x9cONxe2x80x9d time period (that is, the time period for the drinking water to pass the length of the electrode surface) cannot be lengthened, the predetermined chlorine concentration may not be attained for all potential water qualities.
Unexamined Published Japanese Patent Application No. 59-150950 discloses a filter in which electrodes for the electrolysis are packaged to give the sterilizing effect. This filter kills bacteria adsorbed by the activated charcoal or suppresses their propagation by providing a chlorine generator to feed the activated charcoal with active chlorine generated by service water electrolysis. As a result, the active chlorine concentration can be reduced by the activated charcoal after the sterilization to provide sterilized water having minimal chlorine smell.
In this arrangement however, the active chlorine generated by the chlorine generator mounted therein only affects bacteria absorbed by the activated charcoal without being fed downstream. When the drinking water feed is interrupted and the drinking water resides downstream, then bacteria can propagate.
Unexamined Published Japanese Patent Application No. 60-283391 and Japanese Patent No. 2564943 disclose drinking water feeding devices. In these references, drinking water such as the service water introduced from the water source and containing chlorine ions is electrolyzed to produce active chlorine having a sterilizing activity so that electrolyzed water may be fed as the drinking water. The drinking water feeding devices thus disclosed electrolyze service water to generate active chlorine and this service water is reserved in a cistern vented to the atmosphere, or in a water reservoir. However, the cistern vented to the atmosphere or the water reservoir is easily contaminated by aerobacteria. When the cistern is equipped with electrolyzing electrodes, on the other hand, the drinking water is fed intermittently, the feeding being determined by the water level, which is detected by a water level sensor. The chlorine concentration changes with the fluctuation of the quantity of water within the range of the difference between the highest water level and the lowest water level so that a constant concentration of active chlorine cannot be stably generated.
In one aspect, the present invention provides a drinking water feeding apparatus which can ensure a chlorine concentration necessary for sterilizing drinking water of various qualities with a simple construction.
In another aspect, the invention provides a drinking water feeding apparatus which can feed, even for long intervals between feeding of the drinking water, drinking water uncontaminated by bacteria.
In yet another aspect, the invention provides a filter having a chlorine generator packaged therein. This filter facilitates the reduction in size of a drinking water feeding apparatus, an icemaker or a home water purifier when packaged therein.
In a further aspect, the invention provides a drinking water feeding apparatus and a chlorine generator, which enables high electrolysis efficiency, by releasing any gases produced by electrolysis such as hydrogen and oxygen gas generated during electrolysis.
As used in the claims and specification, the term xe2x80x9cactive chlorinexe2x80x9d refers to chlorine-containing molecules which have toxic activity against microorganisms, particularly bacteria, and refers specifically to those chlorine-containing molecules which are produced through electrolysis of chlorine-ion containing aqueous solutions. Such molecules include Cl2, hypochlorous and hydrochloric acids, and species produced therefrom in aqueous solution.
As used in the claims and specification, the terms xe2x80x9cservice waterxe2x80x9d or xe2x80x9ccivil waterxe2x80x9d refers to water as supplied by municipal and other sources, commonly known as xe2x80x9ctap water.xe2x80x9d The term xe2x80x9cfeed waterxe2x80x9d refers to filtered service water. The term xe2x80x9csales waterxe2x80x9d refers to electrolyzed feed water. The term xe2x80x9cdrinking waterxe2x80x9d is synonymous with xe2x80x9csales water.xe2x80x9d
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods and examples are illustrative only, and not intended to be limiting.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.